Hello lilian canale,
I'm aware of the fact that there are no single word equivalents in French, English or German and probably not in Latin either. However, I have been wanting for ages to see a correct and 'elegant' rendering of these terms. I suppose they are concuñado and consuegro in Spanish. In Malay, consogro/consogra are besan (lelaki/perempuan), - both in Indonesia and in Malaysia. Concunhado is biras or ipar besan but I suspect that their frequency is different in each country. In Dutch I use the Malay words which are quite well known amongst Eurasian Dutchmen or else I use medezwager and medeschoonvader (loan translations from Portuguese) which I have coined myself and which seem to work well for the general public. Thank you for your effort.